Change ISP?
Seriously, if they're throttling unknown traffic then you will have a hard time trying to bypass their mechanism - and trying to do so may put you in breach of the terms and conditions.
It's easier to just find another ISP - and make sure you ask about thorottling before you sign up.
Your old ISP might make a fuss about contracts. The local version of "Service unfit for the purpose for which it was sold" is usually enough to shut them up.